Thin film photovoltaic (PV) modules (also referred to as “solar panels”) based on cadmium telluride (CdTe) paired with cadmium sulfide (CdS) as the photo-reactive components are gaining wide acceptance and interest in the industry. CdTe is a semiconductor material having characteristics particularly suited for conversion of solar energy to electricity. The junction of the n-type layer and the p-type layer is generally responsible for the generation of electric potential and electric current when the CdTe PV module is exposed to light energy, such as sunlight. Specifically, the cadmium telluride (CdTe) layer and the cadmium sulfide (CdS) form a p-n heterojunction, where the CdTe layer acts as a p-type layer (i.e., a positive, electron accepting layer) and the CdS layer acts as a n-type layer (i.e., a negative, electron donating layer).
A transparent conductive oxide (“TCO”) layer is commonly used between the window glass and the junction forming layers. This TCO layer provides the front electrical contact on one side of the device and is used to collect and carry the electrical charge produced by the cell. Conversely, a back contact layer is provided on the opposite side of the junction forming layers and is used as the opposite contact of the cell. This back contact layer is adjacent to the p-type layer, such as the cadmium telluride layer in a CdTe PV device.
An encapsulating substrate is positioned on the opposite side of the device to encase the thin film layers between the window glass and the encapsulating substrate. The encapsulating substrate typically contains a hole that enables connection of the photovoltaic device to lead wires for the collection of the DC electricity created by the PV device. However, since PV devices are typically used outside, the PV devices are subjected to varying environmental conditions and exposed to humidity, dew, rain, and other moisture exposure. The hole in the encapsulating substrate can be particularly susceptible to moisture ingress into the device. Such moisture can reduce the efficiency of the PV device and significantly shorten its effective lifespan.
As such, a need exists to inhibit and prevent moisture ingress into the PV device, particularly at the hole in the encapsulating substrate.